This is a proposal to conduct a pharmacokinetic and pharmacodynamic study of methadone. An oral dose, 0.2 mg/kg, will be taken by an equal number of healthy male and female volunteers (6 of each gender) on a single occasion. Blood will be sampled at multiple time points out of 96 hours after the dose for lab measurement of the plasma concentration of methadone's separate isomers and the extent of their plasma protein binding. The overarching goal of this research is to predict the dose of methadone for an individual pregnant addict based on data obtained from randomly collected blood samples early in the women's pregnancy that would result in a minimal neonatal withdrawal syndrome while maintaining the mother's opiate dependence. This currently proposed study will collect the initial pilot data toward achieving this goal.